1. Field of the Invention
The present invention relates generally to a feeder mechanism for a mobile robot, and more particularly to application of the feeder mechanism to a library apparatus having a plurality of cells each for storing a cartridge in which a recording medium is contained.
2. Description of the Related Art
A library apparatus has a plurality of cells each for storing a cartridge such as a magnetic tape cartridge and an optical disk cartridge in which an information recording medium is contained. The cartridge stored in any cell selected from the plural cells is loaded into a drive unit provided in the library apparatus. Then, information processing is carried out on the medium contained in the loaded cartridge by the drive unit. More specifically, information recording and/or reproduction is carried out on the medium by the drive unit.
The library apparatus usually has a cartridge accessor station (CAS) for allowing insertion and ejection of the cartridge. The library apparatus further has an accessor robot acting on the cartridge to transfer the cartridge among the cartridge accessor station, each cell, and the drive unit.
In a large-scale library apparatus, the accessor robot is moved along at least one straight line specifically in a horizontal direction to enable efficient transfer of the cartridge. For example, in a library apparatus described in Japanese Patent Laid-open No. 8-235729, an accessor robot is moved by a drive force of its own motor along a straight rail extending in a horizontal direction.
To supply electric power to the accessor robot or transfer a control signal, a feeding cable is connected to the accessor robot. In a large-scale library apparatus, the accessor robot moves over 20 m in some cases, and accordingly the feeding cable tends to become long, so that a special feeder mechanism attempts have been made to remove this tendency long feeding cable.
To apply a given tension to the cable and thereby prevent slack of the cable irrespective of a moving position of the accessor robot, a wire rope and an idler pulley (running pulley) may be used. One end of the wire rope is connected to a housing of the library apparatus, and the other end of the wire rope is connected to the accessor robot. When the accessor robot moves a certain distance, the idler pulley moves half the distance. Accordingly, by wrapping the cable around a cable drum moving with the idler pulley, fixing one end of the cable to the accessor robot, and fixing the other end of the cable to the housing, a constant tension is always applied to the cable.
In recent years, a high moving speed of the accessor robot has been required in response to a high access speed. Further, an increase in acceleration of the accessor robot causes significant damage to the wire rope.